why a briny mars is exciting, but isn’t necessarily good news

The good news is that Mars had briny oceans usually perfect for life. The bad news is that the brine contained salts used in rocket fuel...

primordial mars

NASA’s recent big announcement, leaked before it was publicly made, is really quite interesting and offers the strongest evidence yet that Mars does have liquid water that might host life. Odd gullies and wet-looking streaks around the planet’s equator have been scrutinized for years, but after finally managing to get a spectroscope close enough to study them, the data confirms the tell tale signs of extremely salty liquid water, practically a brine, being responsible for these wet streaks on the Martian surface. No matter how they formed, their chemical signatures require a non-trivial amount of liquid to be present throughout the process, and this discovery means that something dynamic is happening under the surface where living things could be safe from a UV bombardment that has seemingly sterilized the surface. This means the next probe we send is going to be looking for alien microbes in Martian caves and will be planned and built post haste now that we know where to look and have the strongest indication yet of possible life, right?

Well, maybe not. One of the big catches is that while we now know there’s liquid water on Mars and that it has a visible effect on the surrounding environment, we don’t know in what form it is, and whether there are sub-surface aquifers or it’s a side-effect of another process. Without any direct signs of persistent water we don’t actually have a great indication for potential life. And as the water that does exist must be briny to avoid freezing solid right away, it’s full of alien salts, a few of which are actually extremely poisonous to life as we know it. Perchlorate has been found before in massive quantities and we know that whatever oceans Mars once had contained it, so while it may be possible that extremophile bacteria evolved to cope with it in the water and later on survived ever-increasing concentrations as the seas boiled, then froze away, it’s significantly lowering the number and variety of possible organisms we might find. And we can’t rule out the grim possibility that it completely snuffed out life because perchlorate salts break down organic compounds that would’ve been by far the most likely building blocks for Martian microbes.

Another thing to consider is that while Mars could well have large cave networks, giving several alien ecosystems a chance to hide from the windstorms and radiation on the surface, without a source of nutrients and neutral solvents, those organisms couldn’t survive. We don’t know if any of these nutrient sources exist, and whether anything underground could purify Martian brine of its toxic salts, which could prevent more complex life from evolving in what would have been an otherwise safe and stable environment. We would have to figure out what organisms could feed and reproduce in environments rich in the chemicals found on the red planet, and devise a way to explore Martian caves with restrictions imposed on us by the size and power of the robots we can actually launch and operate in mind. Digging to find an existing cave is out of the question, we’d have to find an entrance into one. Likewise, the robots we send would require a degree of independent thought most machines currently don’t have because they would have a very hard time communicating with mission control through the many tons of Martian rock and sand.

Compare the missions that would be required to find a microscopic extremophile colony cluster on Mars with the promise of missions to Europa and Enceladus with vast, warm, salty oceans a lot like ours and offering the chance for complex living things to evolve, and it seems that while looking for signs of life on the red planet would be interesting, the payoff isn’t that great. Again, this is not to rule out that there’s life on Mars, but given the abundance of chemicals we’re very confident are poisonous to every organism with even remotely recognizable chemistry, there is the chance that Mars is no longer a habitable world for anything we would readily identify as an unambiguously living thing. And that’s kind of sad to consider because for the last 200 years, a great deal of scientific literature fixated on Mars having advanced intelligent life which built vast canal systems for global irrigation and erected large cities much the same way we tend to do. If after all that hoping we find out that Mars is now a dead world, emotionally, that would hurt. But that’s science for you. Often times the reality isn’t what you wanted it to be, and with in the very long running hunt for life on red planet it seems that its past was rosier than its present…

# astrobiology // chemistry / extremophiles / mars


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